Graphite as commercialized anode active material cannot meet the needs of the development of lithium ion batteries, because of its low theoretical specific capacity (372 mAh·g−1) and poor high rate charge/discharge performance. The development of lithium ion batteries with high energy and large power are urgent to seek new anode having high capacity, long life, and good safety performance to substitute conventional carbonaceous anode formed by graphite material.
Silicon anode material has been investigated as a promising high capacity anode material, because of its high theoretical specific capacity, and low electric potential of Li+ intercalation and deintercalation. Reversible intercalation of lithium in the silicon is about 4000 mAh/g. But silicon material has a large volume change (volume expansion greater than 300%) in Li+ intercalation and deintercalation process, leading a rapid capacity decrease and a poor cycle performance. Low conductivity and low first coulomb efficiency of the silicon material also restrict its practical application in the lithium ion batteries.
Nano-sized silicon particles is used as the silicon anode material in prior art, to reduce the volume change of the silicon anode material in Li+ intercalation and deintercalation process and improve structural stability and cycle performance of the silicon anode material. But the nano-sized silicon particles are easily agglomerated, which is unable to play the advantages of nanoparticles. In addition, carbon particles are coated on surface of the silicon anode material to improve the conductivity of the silicon anode material in prior art. But combination between the nano-sized silicon particles and the carbon particles is poor, and a plurality of the nano-sized silicon particles are easily agglomerated and directly in contact with each other, which results an uneven coating, and chemical electrical property of the silicon anode material can not be effectively improved.